Friction transmission mechanism for a motor-driven blind

Abstract

A friction transmission mechanism for a motor-driven blind is constructed to include a driving unit, and at least one cord roll-up unit controlled to the driving unit to lift/lower or tilt the slats of the motor-driven Venetian blind. Each cord roll-up unit includes an amplitude modulation wheel controlled by the driving unit to lift/lower the slats and bottom rail of the Venetian blind, a frequency modulation wheel for rotation with the amplitude modulation set to tilt the slats of the Venetian blind, spring elements, which forces the frequency modulation wheel into friction-engagement with the amplitude modulation wheel, and a support supporting the amplitude modulation wheel, the support having a shoulder adapted to act with a protruding block of the frequency modulation wheel and to further limit angle of rotation of the frequency modulation wheel.

What the invention claimed is:  
     
       1. A friction transmission mechanism mounted in a motor-driven Venetian blind for controlling lifting of slats and bottom rail of the Venetian blind and tilting of slats of the Venetian blind, comprising at least one cord roll-up unit and a driving unit adapted to drive said at least one cord roll-up unit, wherein said cord roll-up unit comprises: 
       an amplitude modulation set, said amplitude modulation set comprising a support, an amplitude modulation lift cord connected to the slats and bottom rail of the Venetian blind and adapted to lift or lower the slats and bottom rail of the Venetian blind, and an amplitude modulation wheel rotatably engaged to said support and coupled to said driving unit for free rotation relative to said support to roll up or down said amplitude modulation lift cord upon operation of said driving unit, said support comprising a shoulder at one side thereof;  
       a frequency modulation set, said frequency modulation set comprising a frequency modulation lift cord adapted to tilt the slats of the Venetian blind, and a frequency modulation wheel engaged on said amplitude modulation wheel and adapted to roll up or down said frequency modulation lift cord as the amplitude modulation wheel rotates, said frequency modulation wheel comprising a protruding block adapted to act against said shoulder of said support to limit rotation of said frequency modulation wheel within a predetermined angle after the frequency modulation lift cord has been rolled up or down; and  
       a linkage, said linkage comprising spring means mounted in between said support and said frequency modulation wheel and forcing said frequency modulation wheel against said amplitude modulation wheel to produce a friction resistance that causes said frequency modulation wheel to be rotated with said amplitude modulation wheel upon rotary motion of said amplitude modulation wheel.  
     
     
       2. The friction transmission mechanism as claimed in  claim 1 , wherein said driving unit comprises a reversible motor, a transmission shaft coupled between said reversible motor and said amplitude modulation wheel and driven by said reversible motor to rotate said amplitude modulation wheel, said transmission shaft having a non-circular cross section fitted into a non-circular axial center through hole of said amplitude modulation wheel, a signal transmitter adapted to transmit control signal, a signal receiver adapted to receive control signal from said signal transmitter and to control operation of said reversible motor subject to received control signal. 
     
     
       3. The friction transmission mechanism as claimed in  claim 2 , wherein said signal transmitter is a remote controller. 
     
     
       4. The friction transmission mechanism as claimed in  claim 2 , wherein said signal transmitter is a wired controller. 
     
     
       5. The friction transmission mechanism as claimed in  claim 1 , wherein said spring means is a coiled spring. 
     
     
       6. The friction transmission mechanism as claimed in  claim 5 , wherein said amplitude modulation wheel comprises a conical end portion disposed in the periphery thereof at one end and adapted to guide winding of said amplitude modulation lift cord around said amplitude modulation wheel. 
     
     
       7. The friction transmission mechanism as claimed in  claim 2 , further comprising a detector adapted to cut off a power supply from said reversible motor when the slats of the Venetian blind are lifted or lowered to an upper limit or a lower limit position. 
     
     
       8. The friction transmission mechanism as claimed in  claim 7 , wherein said detector comprises a mounting plate fixedly mounted in the Venetian blind, a locating block fixedly supported on said mounting plate, a wheel supported in said locating block and coupled to said driving unit for rotation and axial movement upon operation of said driving unit, and two limit switches disposed at two sides in an axial displacement path of the wheel of said detector and electrically connected to said driving unit and adapted to cut off power supply from said driving unit when touched by the wheel of said detector. 
     
     
       9. The friction transmission mechanism as claimed in  claim 8 , wherein said limit switches are respectively disposed in positions corresponding to the upper and lower limit positions of the lifting or lowering of the slats of the Venetian blind.